Effect of zone pressure on wafer bending and fluid lubrication behavior during multi-zone CMP process

Abstract

Graphical abstractDisplay Omitted Wafer bending and fluid pressure are measured during 12-inch multi-zone CMP.Multi-zone carrier has zone-loading effect on wafer bending.Zone pressure configuration affects wafer bending and fluid pressure.Convexly-bended wafer generates the largest fluid pressure due to a suitable wedged gap.Higher edge zone pressure contributes to concave bending and lower fluid pressure. In situ wafer bending and interfacial fluid pressure measurements for a 12-inch multi-zone chemical mechanical polishing (CMP) are reported over a range of zone pressures from 0 to 2.0psi. Effects of zone pressure configurations on wafer bending and interfacial fluid pressure were studied using a novel in situ measurement system. The individual zone pressure loading tests confirm that the multi-zone wafer carrier has obvious zone-loading effect on wafer bending. The multi-zone loading tests reveal that different zone pressure configurations may result in different wafer bending profiles and fluid pressures during CMP: with the constant mean zone pressure of 1.0psi, compared with the normal deformed wafer under uniform zone pressures, center-higher zone pressures generate convexly deformed wafer, and the largest fluid pressure, supporting 32% of the downforce; while edge-higher zone pressures trend to produce concavely deformed wafer, and the lowest fluid pressure. Particularly, edge zone pressure has obvious effect on wafer edge bending profile, higher edge pressure leads to concave deformation of the wafer edge, as a result, the fluid pressure decreases with an increase in edge zone pressure. It is expected that this study can give assistance to the process control of multi-zone CMP.